This invention relates generally to a waste peeling apparatus for separating the waste part of a continuous web material (or web waste) from the continuous web material (or web).
In the manufacture of labels, a laminated web, having an upper layer over-lying a substrate, is fed from an unwind roll to the processing machine. The web is such that the upper layer is adhered to the substrate by a suitable adhesive, but is easily stripped or peeled from the substrate without damage to either layer. The compositions of the layers are such that nearly all the adhesive remains with the upper layer so that a label can be peeled off the substrate and then placed on the object to which it is to be applied such as a container or the like.
The processing machine into which the laminated web is fed, may have several stations which perform various operations on the web as the web travels there-through. For example, there may be one or more printing stations, cross-perforating, line hole punching, die-cutting, and matrix stripping. It is the matrix stripping operation to which this invention relates.
In a die-cutting station, the upper layer of the web is die-cut by a rotating die and/or reciprocating dies which penetrates the laminate but not the substrate. This leaves a die-cut pattern defining the shape of the labels, and a waste matrix or web waste. At a stripping station, the waste matrix is removed or separated from the web leaving only the substrate and the label portions which may then be further processed onto a rewind roll, by folding, by sheeting, or the like. It is readily appreciated that productivity is directly related to machine speed, and that the machines can be operated at a speed only as fast as the station with the least capability. Thus, if one station cannot exceed a certain speed, the entire machine will have to be run at that speed even though other stations will operate faster. One of the weak links as far as operating speed is concerned has been the stripping station, and this is particularly so where the waste matrix is relatively weak.
The configuration and strength of the waste matrix depends on the die pattern which, because of some job requirements, leaves a relatively weak matrix that breaks quite easily or tends to xe2x80x9cridexe2x80x9d to the center of the rewind roll. For example, if the matrix includes vertical strands of substantial width, its strength will be sufficient to allow relatively high speed operation, but if there are very few longitudinal strands and they are quite thin, the matrix will easily break and the speed of the machine will have to be reduced substantially to prevent such breakage. Also, if there are only two outside longitudinal strands with no longitudinal strands therebetween, these strands tend to move toward each other causing the waste matrix roll to bulge at the center.
FIG. 1 shows a waste peeling apparatus or stripper according to the prior art. Web 1, entering from the left side as seen in FIG. 1, passes over guide rollers 2 and reaches peeling roller 3. At this point, web material 1a is separated from waste matrix 4, and is transported from guide roller 5a, around and in contact with a non-slip outside surface of drive roller 7, which is rotationally driven by a variable speed drive motor 6, and then around guide roller 5b to a next process, such as a rewinding process.
While the speed of web 1 can be adjusted by drive motor 6, tension must be applied in order to stably transport the web 1 and stably separate the waste matrix 4 from web 1. One way of applying this tension, shown in FIG. 1, is with a brake roller shaft 8 having an outside surface of a non-slip material, such as cork. Rotation of shaft 8 is adjusted by means of a magnetic particle brake 9. This adjustment maintains appropriate tension on web 1 from the brake roller shaft 8 to the drive roller 7, and enables the waste matrix 4 to be stably separated from the web 1.
After the waste matrix 4 is separated by peeling roller 3, which is positioned where the tension on web 1 is stable, waste matrix 4 is wound around the outside of a waste take-up core 12 mounted on a waste take-up shaft 11 that is driven by a torque motor 10, thereby forming a waste roll 13 of waste matrix 4.
Because of problems with its strength, the separated waste matrix 4 can not be stably wound up by applying high tension to the waste matrix, as is possible with other common roller materials. As a result, some means is conventionally used to prevent excessive take-up drive tension from being applied to the waste matrix 4 after separation, such as, taking up the waste matrix 4 using a torque motor that slows rotation when the load exceeds a set torque level.
As shown in FIG. 2, a large part of the separated waste matrix 4 is generally a structure of consecutive holes 4x of which the perimeter is defined by narrow border or longitudinal members 4y and cross members 4z. Because the waste take-up shaft 11 is conventionally disposed to the other rollers 2, 8, 5a, 5b, 7, tension for separation can only be applied to the waste matrix 4 in the direction of the arrows, that is, only to longitudinal members 4y, when separating the web 1 and the waste matrix 4, and cross member 4z is separated only by indirect force transmitted as an effect of the tension on longitudinal member 4y. As a result, separation is delayed at the middle of cross member 4z where the tension effect of the longitudinal member 4y is least, and cross member 4z can not be evenly and simultaneously separated from web 1.
A peeling roller or stripper 3, or fixed member such as a separating plate, is interposed for actual waste separation, as shown in FIG. 3, for the purpose of assisting separation. However, when the waste matrix 4 is shaped as shown in FIG. 3, and particularly when the longitudinal members 4y are narrow and the cross member 4z is long, the waste matrix 4 twists due to the delayed separation of the cross member 4z. Stress concentrates at A, and the waste matrix 4 tears easily.
Various efforts have been made to resolve this problem, including making the longitudinal members 4y wide enough so that the waste matrix 4 does not tear easily, or reinforcing the waste matrix 4 by including fibers in the web material. Such measures are, however, expensive and time consuming, and are, therefore, only used in limited applications. It is, therefore, difficult to increase the efficiency of the overall process because the waste matrix 4 must be separated at a speed that will not cause the waste matrix 4 to tear. More particularly, when the shape of the waste matrix 4 makes tearing especially easy, it may be necessary to remove the waste matrix 4 manually rather than using a peeling machine to separate the waste matrix 4. This requires much manual labor to peel and then dispose of the waste matrix 4, which becomes very bulky after it is peeled and manually wound up.
With the prior art peeling methods, there is also a strong possibility that the product 14 will also be picked up, as shown in FIG. 4, in conjunction with the waste matrix 4 when the waste matrix 4 is peeled. Attempts to resolve this problem have included using an acute peeling angle B and modifying the shape of the peeling roller 3. However, while product pickup become less likely with as the peeling angle becomes more acute, the waste matrix 4 tends to tear more easily with more acute peeling angles. The problem of this product pickup and the problem waste matrix tearing thus conflict with each other.
The foregoing illustrates limitations known to exist in present waste matrix strippers. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.
In one aspect of the present invention, this is accomplished by providing a stripper for separating a waste matrix from a web, the stripper comprising: a waste matrix peeler positioned at a skewed angle to the direction of travel of the web; and a waste matrix guide roller positioned laterally sideways from an edge of the web.
It is a primary purpose of the present invention to provide a method and apparatus for stripping the matrix from the web at speeds substantially greater than with the conventional method with a corresponding increase in productivity, and where the tendency for the rewind matrix roll to bulge is greatly reduced if not eliminated.
A means whereby the present invention achieves these objects is removing the waste matrix at an angle that is diagonal to the direction of travel of the web and then travels at an angle that is not perpendicular to the axis of the guide rollers, waste matrix cross members are peeled from the web with substantially no delay relative to the longitudinal members. It is therefore possible to significantly reduce the potential for tearing and at the same time resolve the problem of product pickup because the peeling angle can be made more acute.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing figures.